An intake and exhaust valve combination is required for downhole pumps in order to provide a means for intaking fluid and providing a seal against backflow of the formation fluid, while at the same time providing means for exhausting fluid while providing a seal against backflow of the exhausted fluid.
Coberly, U.S. Pat. No. 2,081,222, sets forth a valve assembly for fluid operated pumps. The valve is comprised of spring loaded caged balls positioned on opposite sides of a plate element which includes a valve seat thereon such that the balls alternately sealingly engage the seat during reciprocation of the pump disclosed therein.
Roeder, U.S. Pat. No. 4,032,266, discloses an improvement over the Coberly valve assembly by the provision of a unique valve seat and cage assembly which cooperates with the ball check valve thereof.
In each of the above valve assemblies, the metal to metal contact between the ball and seat causes rapid wear to occur, especially when contamination with abrasive material takes place within the pump. Production of sand cuts the metal seating surfaces. The plurality of expensive balls are sometimes chipped, pitted, or washed into an oblated configuration by the flowing production fluid.
Sometimes production conditions are encountered wherein the balls are impacted in a peculiar manner against the seat, called pounding, whereupon the balls, followers, housing, and seats are destroyed and continued pumping action rapidly wears the pump because of the absence of lubricant therewithin.
Accordingly, it is desirable to have made available an improved intake and exhaust assembly for a downhole pump which eliminates balls, seats, springs, and other mechanical moving metal parts. It is desirable that such an apparatus be inexpensive, efficient in operation, and less likely to encounter the above mentioned problems peculiar to the present metal ball and seat valve assembly of the prior art.